Poly(phenylene ether) is a type of plastic known for its excellent water resistance, dimensional stability, and inherent flame retardancy. Properties such as strength, stiffness, chemical resistance and heat resistance can be tailored by blending it with various other plastics in order to meet the requirements of a wide variety of consumer products, for example, plumbing fixtures, electrical boxes, automotive parts, and insulation for wire and cable.
Some applications for poly(phenylene ether)-based resins require significant flame retardant capability. Examples include applications in the construction, transportation, electronics, and solar power industries. Poly(phenylene ether) is inherently flame retardant, but it is often blended with impact modifiers that reduce the flame retardancy of the resulting composition even as they improve its processing and mechanical properties. So, flame retardant additives are often required for blends of poly(phenylene ether)s with impact modifiers.
When the application requires a flammability rating of V-1 or V-0 in the 20 millimeter Vertical Burning Flame Test of Underwriter's Laboratory Bulletin 94 “Tests for Flammability of Plastic Materials, UL 94”, relatively large amounts of flame retardant additives, especially organophosphate esters, can be required. These large amounts of organophosphate esters can unacceptably reduce the heat resistance of the composition. Also, large amounts of organophosphate esters can exacerbate smoke generation by the composition. Halogenated flame retardants are one alternative to organophosphate esters, but health and safety-based regulatory constraints increasingly discourage or forbid their use.
Accordingly, there remains a need for impact-modified poly(phenylene ether) compositions that exhibit a UL 94 V-1 or V-0 flammability rating along with good impact resistance and heat resistance while containing little or no organophosphate ester or halogenated flame retardant.